Designing a pond

How to get the design and planning stage right first time.

Building ponds

Where, how and what materials and equipment. The hard work bit.

Koi Pond Pumps

How to choose and where to buy your koi pond pump.

Koi Pond Filters

Selecting the correct filter for your koi pond.

Koi Pond Food

Choosing the right food to keep your koi fit and healthy.

Koi Pond UV Clarifiers and Sterilisers.

UV ClarifierYou may think that a UV clarifier or steriliser isn't necessary, or it can wait until later on after building your pond. And of course this is true, it isn't essential for the running of your pond's filter system. However it will enhance and improve your Koi pond . UV is short for ultraviolet and is used to kill off the algae that makes your pond water green. This must be good for the koi mustn't it? Well, yes and no. In actual fact, green water is actually good for your Koi. It helps to protect them from over exposure to sunlight and contains high levels of natural nutrients.

Of course, that doesn't mean to say that we, as koi keepers, want to maintain a nice green pond for our koi. We actually go to all of this expense of a koi pond so that we can enjoy their colours and watch them feed. Also, Koi sometimes develop illnesses which need to be spotted as soon as possible, which is easier to do in good clear water. So we agree that a clear pond is the way to go and to do this we need to install UV.

There are two types of UV unit available:

UV clarifiers

  • Kill off the algae that causes green water
  • have no effect on reducing blanketweed growth
  • A 50W UV unit will cost around £110

UV sterilisers

  • Sterilise pond water
  • kill up to 99.9% of certain viruses, algae, spores and bacteria
  • have no effect on reducing blanketweed growth
  • Usually made form stainless steel, allowing UV light to be reflected inside the unit to improve performance
  • Need matching to the flow rate of filter system
  • UV sterilisers are larger than UV clarifiers
  • Considerably more expensive – from £400 upwards
  • Replacement bulb costs also significantly higher

Both types of UV unit expose the water flowing through it to ultraviolet light. The UV bulb is housed within a quartz tube, protecting it and the electrical connections from coming into direct contact with the water. Quartz is used as glass actually blocks some of the UV light from penetrating the water as it flows through the unit, whereas quartz does not.

UV units are installed on the pipework so that the water is pumped through it. Some filter systems have UV already built in to them. The position of the UV unit within the filter system is not critical except in pressure filters in which case it must be fitted after the pressure unit, otherwise the pressurised water may damage the unit.

So, before you buy a unit, you will need to know the gallonage of your pond. You will need 10W of UV light for every 1,000 gallons of water. Think about where you will install your unit. Don't forget, you will need access to mains power. Also bear in mind that most units are not waterproof and should not be installed anywhere liable to flood.


The UV bulbs will need changing at least once a year, and preferably every six months, regardless of whether they look clean and still produce light. The best time to change the bulb is March. This way, it will function at 100% throughout the summer months when green water is at its worst. UV light can damage your eyes so turn it off at the mains when you’re maintaining the unit.

When changing the bulb, take the opportunity to clean the quartz sleeve as they soon get dirty and limescale may have built up. You will need to remove the bulb to do this. Be very careful as they are fragile.

Hozelock Vorton 27000

UV ClarifierClear water for ponds up to 27000 Litres.

One of the most advanced UVC's available.

The Vorton incorporates a special turbulator that forces the water to flow round the UV in a corkscrew like motion.


  • Employs more efficient single ended UV bulb
  • Guaranteed clear water when used to manufacturers instructions
  • Max Pond Size: 27000 litres
  • Max Flow: 13500 lph
  • UV Wattage: 22 w
  • Inlet Size: 20-40 mm
  • Running Costs: 22 watts


see the whole range at pondkeeper.co.uk

Filtoclear 15000

UV ClarifierCombined filter and UVC Clarifier

This quality model combines innovative filter technology with effective UVC clarifying. In addition it is equipped with the unique and user friendly Easy Clean Technology, which makes cleaning the filter simple.

Premium pressurised filter with German engineering. Fantastic "Easy-Clean" system: simply agitate the sponges up and down using the exterior handle and the dirty water can be exited to a drain/flowerbed.

oaseThis quality model combines innovative filter technology with effective UVC clarifying. In addition it is equipped with the unique and user friendly Easy Clean Technology, which makes cleaning the filter simple.


  • Built in UVC
  • Fine mechanical and large pore biological filter elements
  • multi directional valve for cleaning
  • Max Pond Size:  12000 litres
  • Max Flow:  15000 lph
  • UV Wattage:  11 w
  • Inlet Size:  20 - 40 mm
  • Running Costs:  11 watts.

available from Pondkeeper £344.99

see the whole range at pondkeeper.co.uk









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